1. Field of the Invention
This invention relates generally to bicycle brakes and their construction, assembly and improved operating capabilities.
2. Description of the Prior Art
A common problem with bicycle brakes of conventional type is that the mounting bolt for caliper-type brakes, normally of approximately 6 mm diameter, flexes under the stress of braking. Under braking stress the front bolt flexes upwardly and the rear one downwardly. A larger, stiffer bolt generally is not used because at the front it would require a larger hole in the fork crown, one of the already most highly stressed parts of a bicycle, and thus weaken it even further, which is highly undesirable, and at the rear, a larger bolt would just about sever the skimpy brake bridge of the bicycle. Therefore, these generally 6 mm bolts are common in the present state of the art. Furthermore, these 6 mm bolts also serve as pivot bearings on side pull brakes, which is a fairly inadequate size. Several companies have used slightly larger bolts of 1/4" (0.014" larger) on a section outboard of the 6 mm part that actually goes through the bicycle frame, and another company uses 8 mm (0.315") on this enlarged portion. However, in both cases the bolt itself which passes through the frame is still 6 mm where it leaves the bicycle frame, and, of course, that is where it starts bending.
Another problem with known type brake assemblies is that the caliper arms of conventional side-pull type have a cross-section that is approximately a 1/2" half-round, such shape, of course, being very inefficient. When the brake is applied standing still, the arms are stressed only in the plane of the cable pull. Of course, the half-round section is stiffest in this direction, though, in fact, not really very stiff. However, when the bicycle is moving and the brake is applied, the rim of the wheel, of course, tends to drag the caliper arms forward very hard. In this direction the cross-section is very weak and inefficient.
This cross-section is also very weak in torsional resistance, so that during hard braking the arms twist enough to change the contact between brake pad and rim so that the rearward end of the brake pad contacts the rim far harder than the rest of the brake pad, thus causing grabbing and jamming.
Furthermore, the standard way of adjusting center-pivoted brakes for "reach", which is the distance from the mounting bolt hole to the side of the wheel rim, is with flattened lower ends of the caliper arms having vertical slots therethrough so that the brake shoes can be shifted vertically within the range of said slots. The pre-flattened and slotted area is still weaker torsionally, which limits its length and therefore the "reach range" of the brake, so that two sizes of brake are needed to cover the different bicycle configurations in general use.
Furthermore, providing a long, flattened, slotted end on the caliper arms means that the extra unneeded length will project below the brake shoe and be unsightly.
Furthermore, in order to clear an occasional fender, or an extremely fat tire, the arms sweep far outward and then back in toward the rims. In addition, the brake pads generally are far thicker than necessary and normally are discarded after less than 50% have been used. Such thick pads also increase the very strong twisting force on the caliper arms because they are so far from a line drawn from arm pivot to rim side. Furthermore, this multi-directional flexing is even worse on center-pull assemblies. The mounting bolt still flexes where it exits the bicycle frame and the arm bridge or U-bracket flexes in the same direction. When the brake shoes touch the rim of the bicycle wheel, the bracket flexes in the same direction, and when the shoes touch the rim, the two caliper arm pivot studs flex outward and upward, and while the lower portion of the arms is short, it is also usually slender so that it flexes and twists.
Another problem with known type brake assemblies is that the brake pads as mounted on the ends of the caliper arms tend to engage the bicycle wheel rim in an unbalanced manner, and the forward motion of the wheel rim pulls the brake pads and shoes forward causing the caliper arms to twist and, therefore, the brake pads are tilted so that only their rearward ends touch the rim. To compensate (at least partially) for such twisting, knowledgeable brake mechanics oftentimes twist the caliper arms with a wrench so that the forward ends of the brake pads contact the rim first. Then when the arms are twisted by wheel motion, the pads rotate and contact the rim flatly. However, most brake manufacturers have totally ignored this need for a "toe-in" adjustment.
Another problem with conventional type caliper arms is that the bearing bore length is so short at the pivot area that the hole actually stretches during braking, allowing further arm movement, and the primary arms, which are not stressed any way except in line with cable pull, are about twice as heavy as intelligent design would have made them. Furthermore, the half-round shape of the caliper arms is about as inefficient as could have been devised for the upper arm.
Another problem is in the cable attaching hardware. Generally, in order to manufacture the arms as cheaply and easily as possible, the upper arms are more or less flat and the cable hardware projects sideways out of the arm ends. Thus, the cable pull (and push) tilts and jams the hardware pieces. Oftentimes the hardware pieces have an incredible number of subcomponents, as many as nine pieces being used in some equipment.
Because in the past conventional type bicycle brakes worked so poorly and had such weak, flexible parts, it was necessary to generally ride with the pads quite close to the wheel rims so that there would be plenty of lever travel available, no matter how hard one squeezed and how much the entire system flexed, stretched, "sponged", etc., and the lever hopefully would not bottom out on the handlebar. Logically, there should be as little lost motion or "sponge" in the system as possible, and once the pads contact the rim firmly, the braking effect should be controlled by how hard the brake handle is squeezed, and not by how far a spongy lever is moved.